Aussie, build that motor back stock. Don't raise the compresion any above fatory. They had issues with preigniton back when we had good gas and revised the spark timing back 4 degress. Leave the cam alone, use a good rocker system. The performer head is a good idea, you won't have dissimular expansion rates like the cast iron head to aluminum block. You may have to increase the size of the heat exchanger to handle the increased heat transfer from teh aluminumhead. Recurving the distributor isn't going to help as most of the total timing is in before you get to cruising rpm, increasing the curve below planning speed can cause preignition. Buy those other two motors you had listed, use the 4bbl intake and oil cooler off of one of those. Put a pertronix igniton in the distributor and a 1 step colder plugs. You will be happy at the peformance with the 3.7 in its stock form. If you want to go faster, put a V8 in the boat. Most of the mods you have listed will work great if the engine was in a car, but in a boat, you will have longevity issues, along with peaky peformance(especially with a heavy boat like a V), don't try to turn the motro any higher than 5000 rpm, the drives don't like high rpm. You'd be surprised how well the boat will perform in stock good condition. I understand your desire to build it bigger and better, but I don't think you are going to get the return from your time and money you are looking for with this combo.
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